Electrical wiring of redox enzymes, a novel basis for making biosensors, provides a powerful method of directly electrically sensing lactate. Biosensors based on the wired enzymes have advantages in accuracy, sensitivity, speed, no leachable components, insensitivity to variation in oxygen partial pressure, insensitivity to interferants, miniaturization (high signal level and small sample size), high stability, and small associated electronics. The specific aim of the Phase I research is to develop such a lactate sensor for use in plasma and serum. Experiments thus far have been conducted in buffer solution; related work on "wired" glucose enzyme electrodes has been successful in serum and plasma. The long term objective is to develop a sensor suitable for use in in vitro blood gas/electrolyte monitors commonly used in cardiac units and for possible incorporation into pulmonary artery catheters that are used to measure blood O2 and CO2 levels and other parameters. Blood lactate concentrations are a sensitive marker for inadequate oxygen utilization and hence of cardiovascular or metabolic failure in critically-ill patients. If the patient is recovering from major cardiovascular or trauma surgery, a rise in blood lactate during recovery may guide the level and type of care required.